Purpose:
Remodelling of the posterior sclera accompanies myopia, and in young guinea pig eyes, early changes occur in the peri-papillary zone (PPZ) around the optic nerve. We examined the differential expression of genes in the PPZ sclera to identify significant pathways associated with myopia.

Methods:
One eye of guinea pigs (n=3) was form-deprived for 2 weeks (day 6-20) using a translucent diffuser to induce myopia. The other eye was untreated and served as a matched control. At the end of 2 weeks, refractive error was measured in cyclopleged eyes using a Nidek auto-refractor. Posterior scleral punches (4 mm) were collected from the PPZ from myopic and control eyes. Total RNA was extracted using an RNeasy® Fibrous tissue mini kit. RNA was sequenced by a commercial provider using an Illumina HiSeq 2000 platform. RNA-seq data were analysed using three different statistical programs (CuffDiff, edgeR and Voom) and the most differentially expressed genes (p value < 10-3) were used to identify significant pathways.

Results:
Form-deprivation induced relative myopia in all animals. The mean difference between myopic and control eyes was -3.76±0.6 D at the end of the treatment period. The number of genes differentially expressed between myopic and control sclera were 26,088, 14,301, and 14,298 using CuffDiff, edgeR and Voom analysis tools, respectively. Differences in gene expression (p<10-3) were found for 850 (CuffDiff), 794 (edgeR) and 270 (Voom) genes using the different analysis programs. Pathway analysis conducted on significant genes identified more than 50 different pathways, of which four have previously been reported as associated with myopia.

Conclusions:
Number of differentially expressed genes were identified in the posterior myopic sclera compared to non-myopic eyes, which varied between analysis packages. Several signalling pathways were consistently identified across the different analysis programs with some of these having previously been identified as associated with myopia in humans and animal models. These findings provide insights into potential pathways involved in active scleral remodelling. Further targeted investigation of these genes may provide potential avenues for development of treatment therapies.<br />